Equipment and line failures in a communication network can cause the undesired loss of data. Consequently, industry has produced various mechanisms to mitigate the effects of such failures. One mechanism entails providing a working bandwidth and a protection bandwidth for communications through the network. The protection bandwidth provides an alternative means for delivering communications through the network should the working bandwidth fail. When there is a failure, the network switches over from the working bandwidth to protection bandwidth, referred to as a switchover.
In some instances, the same line (i.e., physical interface, e.g., fiber) carries the working and protection bandwidth, thus a single line cut defeats the protection offered by the protection bandwidth. Even if the working and protection bandwidths are provisioned on separate lines (i.e., a working line and a protection line), typically these lines are physically proximate to each other or traverse the same network equipment. Injury to one line can affect the other line because of their physical proximity, thus impacting both the working and protection lines. Similarly, the failure of network equipment that handles both the working and protection lines can disable both lines.
There are also various techniques for achieving a switchover in the event of a failure. In one technique, the protection line does not carry real traffic until the transmitting end learns of the failure and of the subsequent switchover. In this instance, despite the redundancy, data is lost until the transmitting end diverts real traffic to the protection line.
In another technique, the working and protection lines provide redundancy by simultaneously carrying the same traffic. Here, the receiving end does not need to communicate the failure and switchover to the transmitting end because both lines carry the same information. For this technique, each network switching element between the transmitting end and the receiving end participates in the decision as to which of the working and protection lines is the active line. A switchover from the working line to the protection line can occur at any one of these intermediate points. A disadvantage, however, of this type of protection switching system is that the network switching elements are part of the same service provider network. This dependence on a single service provider exposes both the working and protection lines to a single failure of the service provider.
Consequently, there remains a need for an improved protection switching system that not only can achieve protection across multiple paths, but also across multiple service providers.